Kenwood TH 234 Service Manual

The Kenwood TH 234 is a professional-grade VHF/UHF transceiver designed for amateur radio use. This service manual covers technical specifications, circuit diagrams, alignment procedures, troubleshooting guidelines, and maintenance instructions for qualified service technicians. The unit features dual-band operation, cross-band repeating capability, multiple scanning functions, and robust construction for reliable performance in various operating conditions.

1. Technical Specifications 2. Block Diagrams 3. Circuit Descriptions 4. Alignment Procedures 5. Disassembly Instructions 6. Parts List 7. PCB Layouts 8. Troubleshooting Guide 9. Test Equipment Requirements 10. Safety Precautions 11. Service Notes

Technical Specifications

Complete technical specifications for the Kenwood TH 234 transceiver.

Parameter	Specification
Frequency Range	VHF: 136-174 MHz, UHF: 400-470 MHz
Output Power	High: 5W, Medium: 2.5W, Low: 1W
Modulation	16KΦF3E (FM)
Power Supply	7.2V DC nominal (6-16V range)
Current Drain	TX: 1.3A max, RX: 150mA typical
Dimensions	58(W) × 110(H) × 30(D) mm
Weight	Approx. 280g (with battery)
Antenna Impedance	50 ohms
Temperature Range	-20°C to +60°C
Channel Capacity	200 channels (100 per band)

Block Diagrams

System block diagrams showing signal flow and major components.

RF Section Block Diagram: Shows receiver front-end and transmitter power amplifier stages.
IF Section Block Diagram: Details intermediate frequency processing circuits.
Audio Section Block Diagram: Illustrates microphone input and speaker output circuits.
Control Section Block Diagram: Displays microprocessor and control logic.
Power Supply Block Diagram: Shows voltage regulation and distribution.

WARNING! Only qualified technicians should perform service procedures. High voltages may be present.

Circuit Descriptions

Detailed descriptions of major circuit sections and their operation.

Receiver Circuit: Dual-conversion superheterodyne with first IF at 45.05 MHz.
Transmitter Circuit: Phase-locked loop synthesizer with power amplifier stages.
PLL Circuit: TCXO reference oscillator with programmable dividers.
Audio Processing: Compander circuit for improved signal-to-noise ratio.
Control Circuit: Microprocessor-based control system with EEPROM memory.

CAUTION! Static-sensitive components require proper ESD protection during service.

Alignment Procedures

Receiver Alignment: RF amplifier tuning, IF alignment, squelch adjustment.
Transmitter Alignment: Power output adjustment, modulation deviation, PLL lock verification.
PLL Alignment: Reference oscillator adjustment, VCO alignment.
Audio Alignment: Microphone gain, speaker output, compander adjustment.
Test Points: TP1 (PLL lock), TP2 (modulation monitor), TP3 (RF power).
Required Equipment: Spectrum analyzer, frequency counter, modulation meter.
Alignment Software: Kenwood service software version 2.1 or later.
Calibration: Factory calibration procedures for accurate frequency control.

Disassembly Instructions

Step-by-step disassembly procedures for service access.

Tools Required: Phillips screwdriver, plastic spudger, anti-static wrist strap.

Remove battery pack and antenna.
Remove six case screws (two under battery contacts).
Separate front and rear case halves carefully.
Disconnect flex cable connectors from main board.
Remove control board assembly for component access.
Document cable routing for reassembly reference.

Tip: Use magnetic tray for screws and document each disassembly step.

Parts List

Complete component listing with part numbers and descriptions.

Part Number	Description	Qty
X51-1230-01	Main PCB Assembly	1
X51-1231-01	Control PCB Assembly	1
X51-1232-01	Display Module	1
X51-1233-01	VCO Module	1
X51-1234-01	Power Amplifier Module	1
X51-1235-01	Case Assembly	1
X51-1236-01	Keypad Assembly	1
X51-1237-01	Battery Pack	1
X51-1238-01	Antenna Assembly	1

PCB Layouts

Printed circuit board layouts and component placement diagrams.

Main PCB Component Side: Shows component locations and reference designators.
Main PCB Solder Side: Displays solder pad locations and ground planes.
Control PCB Layout: Keypad interface and display connections.
RF Module Layout: VCO and power amplifier component placement.
Test Point Locations: Voltage measurement and signal injection points.

WARNING! Observe proper soldering techniques to prevent PCB damage.

Troubleshooting Guide

Systematic troubleshooting procedures for common problems.

Symptom	Possible Cause	Corrective Action
No power	Battery/connections	Check battery voltage; inspect power switch and DC jack.
No transmit	PA circuit/PLL	Verify PLL lock; check PA bias and output stages.
Poor reception	RF front-end	Check antenna connection; align receiver front-end.
Display issues	LCD/connections	Verify flex cable connection; check LCD contrast voltage.
Audio problems	Audio IC/circuit	Check audio amplifier IC; verify speaker connections.

Reset: Hold [F] + Power to reset to factory defaults.

Test Equipment Requirements

Essential test equipment for proper service and alignment.

Safety Precautions

Critical safety information for service personnel.

CAUTION! RF radiation hazard during transmitter testing. Use proper shielding.

Service Notes

Additional service information and technical bulletins.

FCC ID: K6630402X40. Copyright © 2006 Kenwood Corporation. For technical support, contact Kenwood Service Department at 1-800-536-9663 or visit www.kenwood.com. This manual is intended for qualified service technicians only.